"Refusing to acknowledge or accept when you've lost is to try and deny the democratic process from taking place."
As far as Brexit goes, that argument is now obsolete.
We have fulfilled the democratic result of the referendum and left the EU.
What happened before was due to no one being able to agree on how it should be done.
As for the US, they've just had a plainly very free and fair election, and despite the hollering and stamping of feet, the democratic process will be followed.
Of course, there may be doubt in that process instilled by certain elements, and that could be a serious problem, but it's a different issue.